Phosphonic acid derivatives are used for surface modification on oxidized metals such as Al2O31), TiO22), ZrO23), SiO24), Mica5), stainless(SS316L) 6), nitinol7), hydroxyapatite8), ZnO9), ITO10,11).For a long time, organosilanes have been used to form self assembled monolayer (SAM) on the metal oxide. However, it is not always adaptable in the applications due to the poor stability and polymerization of the reagent with each other. On the other hand, phosphonic acid derivatives equally form a SAM on the metal oxide despite being very stable compounds. Also, phosphonic acid derivatives have been reported to use formation of more stable and dense SAM than organosilanes. Schwartz et. al. shows the phosphonate SAM perform stable and higher density by four times than that of the organosilane in alkaline solution when a SAM of 11-HUPA is formed on Titanium oxide film to modify the fluorescent molecules2). The phosphonic acid derivative mechanistically bind to a high density on titanium oxide film because a phosphonic acid derivative produce OH by a proton transfer to the substrate while an organosilne react only with OH group present in the titanium oxide film12).
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2) B. M. Silverman, K. A. Wieghaus, J. Schwartz, "Comparative properties of siloxane vs phosphonate monolayers on a key titanium alloy", Langmuir, 2005, 21 (1), 225.
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5) J. T. Woodward, A. Ulman, D. K. Schwartz, "Self-assembled monolayer growth of octadecylphosphonic acid on mica", Langmuir 1996, 12 (15), 3626.
6) A. Raman, M. Dubey, I. Gouzman and E. S. Gawalt, “Formation of self-assembled monolayers of alkylphosphonic acid on the netive oxide surface of SS316L E Langmuir, 2006, 22, 6469.
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8) S. C. D’Andrea and Al. Y. Fadeev, "Covalent surface modification of calcium hydroxyapatite using n-alkyl- and n-fluoroalkylphosphonic acids", Langmuir, 2003, 19, 7904.
9) B. Zhang, T. Kong, W. Xu, R. Su, Y. Gao and G. Cheng, "Surface functionalization of zinc oxide by carboxyalkylphosphonic acid self-assembled monolayers", Langmuir, 2010, 26(6), 4514.
10) A. Sharma, B. Kippelen, P. J. Hotchkiss and S. R. Marder, "Stabilization of the work function of indium tin oxide using organic surface modifiers in organic light-emitting diodes", Appl. Phys. Lett., 2008, 93, 163308.
11) A. Pulsipher, N. P. Westcott, W. Luo, and M. N. Yousaf, "Rapid in situ generation of two patterned chemoselective surface chemistries from a single hydroxy-terminated surface using controlled microfluidic oxidation", J. Am. Chem. Soc., 2009, 131 (22), 7626.
12) J. Schwartz, M. J. Avaltroni, M. P. Danahy, B. M. Silverman, E. L. Hanson, J. E. Schwarzbauer, K. S. Midwood, E. S. Gawalt, "Cell attachment and spreading on metal implant materials", Mater. Sci. Eng. C, 2003, 23, 395.